Aryl halides are extremely less reactive towards nucleophilic substitution reaction because of

Resonance effect

The correct answer is Option (2) → Resonance effect

The low reactivity of aryl halides in nucleophilic substitution reactions is mainly due to resonance stabilization between the halogen and the aromatic ring.

Option 1: Electromeric effect Electromeric effect is a temporary effect that occurs only in the presence of an attacking reagent. It does not contribute significantly to the permanent stability of the C–X bond in aryl halides. Hence, it is not responsible for their low reactivity.

Option 2: Resonance effect In aryl halides, the lone pair of electrons on the halogen atom participates in resonance with the aromatic ring. This gives partial double bond character to the C–X bond, making it shorter and stronger. Due to this partial double bond nature, the bond becomes difficult to break, reducing reactivity towards nucleophilic substitution.

Option 3: Inductive effect Halogens show a −I effect which actually increases the partial positive character on carbon and should favor nucleophilic attack. However, this effect is weaker than resonance and does not explain the reduced reactivity.

Option 4: Hyperconjugation effect Hyperconjugation is generally observed in alkyl systems involving C–H bonds adjacent to π systems. It does not play a role in stabilizing the C–X bond in aryl halides.